Silicon-Tethered Strategy for Copper(I)-Catalyzed Stereo- and Regioselective Alkylboration of Alkynes

Stereoselective silicon-tethered alkylboration of alkynes in the presence of a copper(I) catalyst and a diboron reagent provided the corresponding cyclic alkenylboronates in high yields (up to 99% yield) with excellent regio- and syn-selectivities (E/Z = <1:99). The products, which can be considered as the formal alkyne intermolecular alkylboration products, undergo subsequent selective derivatization, including ring opening, to give functionalized trans-stilbene derivatives.